The present invention relates to a semiconductor substrate etching apparatus, and particularly relates to a semiconductor substrate etching apparatus for automatically etching a beveled outer edge of a semiconductor substrate (also referred to as a wafer) having a bevel structure.
A disk-shaped semiconductor substrate having no orientation flat is adopted as a wafer for a large-power semiconductor device. Most of the semiconductor substrates are tapered or beveled at edges thereof to maintain predetermined breakdown voltages. During beveling, cracks and defects are produced in the beveled edge of the wafer, and must be removed by etching the beveled edge.
The etching of the beveled edge of the wafer is conventionally achieved by the following processing. As illustrated in FIG. 5, one major surface of a semiconductor substrate 1 is entirely coated with an antietchant 2 with a brush, and then the semiconductor substrate 1 is bonded to a fluoroplastic disk 3 having the same diameter as the semiconductor substrate 1. Thereafter, the semiconductor substrate 1 is placed on a hot plate 4 through the fluoroplastic disk 3 for baking for several minutes so that the semiconductor substrate 1 and the fluoroplastic disk 3 are adhered to each other. After baking, the other major surface or the pattern formation surface is coated with an antietchant 5 by a brush, and is then similarly baked. Care should be taken not to apply the antietchant to the beveled edge 1a during the antietchant applying operations.
The semiconductor substrate 1 attached to the fluoroplastic disk 3 as illustrated in FIG. 5 is picked up by a tweezers 6, and is immersed in an etchant 7 for a predetermined time to etch only the beveled edge of the semiconductor substrate 1. After etching, the semiconductor substrate 1 is cleaned with water, and is then immersed in a boiling organic solution to peel off the fluoroplastic disk 3 from the semiconductor substrate 1 as well as to remove antietchant 2 and 5. Thereafter, the semiconductor substrate 1 is washed in a water flow. After washing, the semiconductor substrate 1 is dried by an infrared lamp 8.
Such an earlier attempt however raised the following problems: great care should be taken to apply antietchant on the opposite major surfaces of the semiconductor substrate 1 so that the antietchant may not adhere to the beveled edge 1a of the semiconductor substrate 1; a fluoroplastic disk 3 must be bonded to one major surface of the semiconductor substrate 1; removal of the antietchant is needed with the accompanying cleaning and drying operations; a considerable drop in yield of the semiconductor substrate 1 due to nonuniform coating of antietchant 2 and 5; the consumption of the etchant is rather increased since the whole wafer is immersed in the etchant for etching only the beveled edge 1a of the semiconductor substrate 1.
Another attempt to overcome such problems is disclosed in Japanese unexamined patent publication (Kokai) 1(1989)-316936. The semiconductor substrate etching apparatus of this publication is, as shown in FIGS. 8 and 9, provided with a rotary table 9 with a vacuum chuck, and an applying roller 11 with a rotary shaft 10, the roller 11 being disposed in parallel with the rotary table 9. An etchant 13 is supplied from an etchant supply nozzle 12 to an outer circumferential groove 11a of the applying roller 11. A semiconductor substrate 1 is vacuum chucked by the rotary table 9, and the beveled edge 1a fits into the outer circumferential groove 11a of the applying roller 11. With such a construction, the etchant 13 is supplied from the etchant supplying nozzle 12 to the outer circumferential groove 11a of the applying roller 11 while the rotary table 9 and the applying roller 11 are rotated. The etchant 13 is held in the outer circumferential groove 11a due to surface tension, and adheres to the beveled edge of the semiconductor substrate 1 for etching as the applying roller 11 is rotated. After completion of the etching of the whole edge of the semiconductor substrate 1, the supply of the etchant is discontinued, and then pure water is jetted from cleaning nozzles 14 and 15 to clean the semiconductor substrate 1. Finally, the semiconductor substrate 1 is rotated at a high speed for drying.
The semiconductor substrate etching apparatus taught in the Japanese unexamined patent publication 1-316936 is disadvantageous in the following points: it automatizes only the applying of the etchant to the beveled edge of the semiconductor substrates and the subsequent washing, and does not automate the whole line of the etching processing including transferring of semiconductor substrates, applying of the etchant, cleaning with water, baking, etc; and nonuniform coating of the etchant takes place if the semiconductor substrate 1 is eccentrically placed on the rotary table 9.